Shocking!

Here's a cool fact from childhood. You can use the small
electric motor from a toy car (specifically, a Hot Wheels "Sizzler") as a
earphone. All you need to do is leave the small rubber tires on, stick one
of the tires into your ear, and put audio into the motor. The motor is small
enough and the magnets big enough that you get fairly good response in the
audio range, which suprised me. But hey, when you can't find an earphone,
and you're 12 years old...